In a large nonstick ovenproof skillet, heat 1 teaspoon of the olive oil. Add the sausage meat and onion and cook over moderately high heat, breaking the sausage up into small pieces, until browned and cooked through, about 5 minutes. Transfer to a plate. Add 2 tablespoons of the olive oil to the skillet and heat until shimmering. Add the potatoes and cook over moderately high heat, stirring occasionally, until crisp and cooked through, about 5 minutes. Add the kale, season with salt and cook, tossing, until softened, about 2 minutes longer.